Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
WriteNext - The writing application that boosts your writing. Increase focus and writing performance and reduce distractions by separating your creative writing from other activities. Let writing be the only activity you perform in the writing application.
Boostnote - Boostnote is an open-source note-taking app.
Writebox - Writebox is a simple and distraction-free text editor for Chrome and iPhone/iPad.
Standard Notes - A safe place for your notes, thoughts, and life's work
Calmly Writer - Distraction-free text editor for Mac, Windows, Linux and ChromeOS.